This application is aimed at investigating the role leptin plays in puberty. We will study the effects of leptin on the stimulation of reproductive function in prepubertal normal male and female mice. We will determine whether treatment of normal female mice with neutralizing antibodies to leptin delays puberty and blocks the initiation of reproduction. Reproductive hormone levels will be determined in experimental mice treated with lelptin to find out whether these changes correlate with leptin levels at puberty. Furthermore, we will generate transgenic lines of mice that overexpress leptin at different levels and in a tissue-specific fashion. This animal model for lepltin-induced puberty will allow us to correlate various levels of leptin in the circulation with reproductive indexes at reproductive maturation.